1. Field of the Invention
The present invention relates to a frame for illuminating a transparency, which may include translucent matter, such as for back-lighting of photographic or other depictions and, more particularly, to such an illuminated frame which is in the nature of a picture frame and which is both compact in size and efficient in applying light for full illumination or for highlighting, shadowing and other dramatic illumination of the transparency.
2. Description of Related Art and Other Considerations
In the following description, the materials used in the present invention comprise optical lighting and light extractor films, which are obtainable from several sources. However, the preferred materials are those manufactured by 3M Company under its trade name "SOLF" (an acronym for its SCOTCH.TM. Optical Lighting Film) and its extractor film. These and related materials are described, at least in part, in U.S. Pat. Nos. 4,260,220, 4,542,449, 4,615,579, 4,750,798, 4,787,708 and 4,791,450, whose disclosures are incorporated herein as if set forth in haec verba. However, it is to be understood that any like materials, which are obtainable from other sources and can perform equivalently, may be used in the present invention. Nevertheless, because the preferred materials comprise those obtainable from 3M, the following presentation emphasizes their employ, although it is not intended that the present invention be limited thereto.
Existing illuminators or light boxes and their constituent materials, such as are manufactured by or with materials originating from 3M Company, are described in several of its publications emanating from its Special Enterprises Department, 3M Traffic Control Materials Division, numbers 75-0299-6017-8 and 75-0299-6016-0, both dated November 1988, and respectively entitled "3M SCOTCH.TM. OPTICAL LIGHTING FILM APPLICATION BULLETIN THIN LIGHT BOX" and "3M SCOTCH.TM. OPTICAL LIGHTING FILM ASSEMBLY INSTRUCTIONS THIN LIGHT BOX INSERTS."
Such a thin light box and its materials are also described in other 3M publications entitled "SCOTCHLAMP FILM .TM.", number 78-6970-2773-4, "3M SCOTCH.TM. OPTICAL LIGHTING FILM GENERAL THEORY," number 75-0299-6018-6, dated November 1988, "3M SCOTCH.TM. OPTICAL LIGHTING FILM SPECIFICATION SHEET," number 75-0299-5727-3, dated November 1988, "Product Bulletin V-5115" entitled "Scotch.TM. Light Extractor Film V-5115," number 75-5100-0145-8, dated July 1989, and a brochure entitled "Product Information" entitled "Scotch.TM. 467MP and 468MP Laminating Adhesives," number 70-0701-2468-3.
Aspects of such a 3M thin light box are described in two papers entitled "Progress in the development of prism light guides" by Steven G. Saxe, Lorne A. Whitehead and Sanford Cobb, Jr., Proceedings of the Society of Photo-optical Instrumentation Engineers (SPIE), volume 692, pages 235-240 (1986), and in above-mentioned U.S. Pat. Nos. 4,260,220 and 4,615,579 by Lorne A. Whitehead. Two other 3M publications are both entitled "3M BRAND SCOTCH LAMP FILM.TM.." Mention is also made to the other above-referenced U.S. Pat. Nos. 4,542,449, 4,750,798, 4,787,708 and 4,791,450.
Two important materials utilized in the 3M thin light box include SOLF (an acronym for 3M SCOTCH.TM. Optical Lighting Film and sometimes referred to by 3M as "SCOTCHLAMP FILM.TM.") and a light extractor film, both of which are described in one or more of the above publications.
As described, for example, in above-identified 3M publication number 78-6970-2773-4 entitled "SCOTCHLAMP FILM.TM.", the SOLF is defined as a clear 0.022" thick acrylic or 0.020" thick polycarbonate film which is manufactured using a 3M microreprocation process to provide very precise prism grooves on one side and a mirror-like plano finish on the other. According to above-referenced U.S. Pat. No. 4,260,220, these grooves form a light guide which is capable of effectively guiding light by total internal reflection in which its planar inner and outer surfaces are defined as being in "octature."
The light extractor film comprises a diffuse, reflecting material, is utilized when it is desirable to have the light escape from the SOLF, and functions to change the direction of the light rays, causing them to scatter and penetrate the film in the desired areas. Particular reference is also made to 3M SOLF Application Bulletin, number 75-0299-6017-8 which contains information necessary for the design and construction of a thin, back-lit display box using SOLF. The extractor film typically is fabricated with a self-adhering adhesive on one surface.
Thin light boxes constructed according to the above publications are limited to relatively large sizes and wattage. Light is directed into the interior of the box from all sides, and a mirrored surface, for example, of silvered Mylar film, is used at the box end, which is opposite from the light bulb end, to redirect the light back into the interior. The SOLF is arranged so that its mirror-like side always faces the light source. To provide the desired light output from such boxes, a minimum 40 watt fluorescent bulb is required. Such a relatively large fluorescent bulb increases the thickness of the box, having a typical small size of 4' by 6', with a 6" to 12" depth, although some depths may have been reduced to a minimum of 21/2". Furthermore, 3M personnel emphasize that the SOLF surfaces must not be damaged so that the light carrying or light reflective qualities of the box materials will not be diminished. Accordingly, it is not practicable to utilize such a light box for other than large outdoor or other industrial displays. Such boxes are not adaptable or at least easily amenable to home or office use, or as an archival light box such as might be employed in a museum, or as a picture-like frame. It is conventional opinion that smaller sizes are not possible or practicable.